DISPLAY DEVICE HAVING FINGERPRINT RECOGNITION SENSOR COUPLED THERETO
A display device having a sensor coupled thereto according to one embodiment of the present invention comprises: a cover layer; a display panel disposed below the cover layer; an optical layer disposed below the display panel; and an image sensor disposed below the optical layer. The optical layer includes: a microlens array layer including a plurality of microlenses; and an aperture layer which is disposed below the microlens array layer and includes holes each spaced apart from the microlenses by a focal length of the microlens. According to one embodiment of the present invention, a distance from a fingerprint to a fingerprint sensor can be greatly decreased in comparison with a conventional technology. In addition, deterioration of fingerprint image quality due to scattered light can be reduced.
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The present invention relates to a display device combined with a fingerprint recognition sensor, and more specifically, to a display device which improves fingerprint recognition performance of a fingerprint recognition sensor combined with the display device.
BACKGROUND ARTFingerprints are widely used for user authentication in a smart phone or a payment means. For this purpose, a fingerprint recognition device is installed in the smart phone or the payment means, such as a credit card or the like, in many cases. Although a separate fingerprint recognition device is used conventionally to recognize a fingerprint, attempts have been made recently to combine a fingerprint recognition with a display.
For example, in U.S. Pat. Nos. 8,994,690 and 9,336,428, it is configured to recognize a fingerprint by adding an image sensor or a capacitive sensor layer for fingerprint recognition to a liquid crystal display (LCD).
However, in the case of adding a fingerprint recognition sensor to a display, light reflected from a fingerprint should pass through a display layer and arrive at the fingerprint recognition sensor. However, since the distance between the fingerprint and the sensor is relatively long and the light is diffusely reflected by ridges and valleys of the fingerprint, it is difficult to acquire an accurate fingerprint image.
A hole (aperture) having a high aspect ratio is formed on each pixel of an image sensor as shown in US Laid-opened Patent No. 2016/0254312 to solve the problem of diffused reflection. However, since the depth of the hole should have a value close to 200 micrometers to get a high aspect ratio, it is difficult to form the hole in a semiconductor process. In addition, since the distance from the fingerprint to the fingerprint sensor is inevitably long as the hole is deep, brightness of an acquired fingerprint is low.
DISCLOSURE OF INVENTION Technical ProblemTherefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a display device combined with a fingerprint recognition sensor, which reduces the distance from a fingerprint to a fingerprint sensor.
Another object of the present invention is to provide a display device combined with a fingerprint recognition sensor, which allows only the light entering almost vertically, among the light reflected from a fingerprint, to enter a fingerprint sensor.
Still another object of the present invention is to provide a display device combined with a fingerprint recognition sensor, which can be formed merely through a semiconductor process.
Technical SolutionTo accomplish the above objects, according to one aspect of the present invention, there is provided a display device comprising: a cover layer; a display panel disposed under the cover layer; an optical layer disposed under the display panel; and an image sensor disposed under the optical layer. The optical layer includes: a microlens array layer including a plurality of microlenses; and an aperture layer disposed under the microlens array layer and provided with holes spaced apart from the microlenses as much as the focal length of the microlenses. The microlens array layer may be provided with a transparent or translucent substrate and a plurality of microlenses formed to protrude on the top surface of the substrate. The substrate may have a thickness making the distance from the microlens to the hole be equal to a focal length, and the aperture layer may be formed to be attached on the bottom surface of the substrate. According to embodiments, the microlens array layer may be formed to protrude on the bottom surface of the substrate. The substrate may further include a light blocking wall formed between the microlenses and may include a light blocking layer in the portions where the microlenses are not formed.
Advantageous EffectsAccording to an embodiment of the present invention, since a microlens array layer can be formed to have a thickness of several micrometers to tens of micrometers approximately, the distance from a fingerprint to a fingerprint sensor can be reduced greatly in comparison with a conventional technique. In addition, since the microlens array layer can be created through a semiconductor process and mounted on an image sensor, a display device combined with a fingerprint recognition sensor can be formed merely through the semiconductor process. In addition, since only the light vertically reflected from a fingerprint may enter the image sensor, degradation of fingerprint image quality caused by scattered light can be reduced.
The detailed description of the present invention will be described below with reference to the accompanying drawings which show a specific embodiment that the present invention can be embodied as an example. The embodiments are described in detail to be sufficiently so that those skilled in the art may understand to implement the present invention. It should be understood that although the diverse embodiments of the present invention are different from each other, they do not need to be mutual exclusive. For example, specific shapes, structures and features described herein may be implemented in another embodiment without departing from the spirit and scope of the present invention in relation to an embodiment. In addition, it should be understood that the locations or disposition of individual components in each disclosed embodiment may be changed without departing from the spirit and scope of the present invention. Therefore, the detailed description described below does not intend to be taken in a limited sense, and the scope of the present invention is limited by only the attached claims if properly explained, together with all the scopes equivalent to the claims. Like reference numerals in the drawings denote similar or like functions in several aspects.
Hereinafter, a display device combined with a fingerprint recognition sensor according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings.
A display device 1 according to an embodiment of the present invention is provided with a cover layer 100, a display panel 200 disposed under the cover layer 100, an optical layer 300 disposed under the display panel 200, and an image sensor 400 disposed under the optical layer.
Cover glass generally used in a smart phone or the like may be used as the cover layer 100, and tempered glass, plastic or the like may be used. Although it varies depending on the material and design, generally, the cover layer 100 has a thickness of approximately 550 to 700 micrometers. Any display panel having a structure capable of transmitting light to the image sensor 400 like an AMOLED panel may be used as the display panel 200, and an AMOLED display panel generally has a thickness of 350 to 750 micrometers. The optical layer 300 is provided with a microlens array layer including a plurality of microlenses and an aperture layer so that only the light vertically reflected from a finger may be transferred to the image sensor 400. Although a CMOS image sensor may be preferably used as the image sensor 400, it is not limited thereto. In an embodiment, the image sensor 400 is disposed only under a certain region of the display panel 200, and the optical layer 300 is not disposed in the other regions.
Next, the cell structure of a general image sensor will be described with reference to
Although it is the better if the size of the hole 321 is the smaller, if the size is too small, a light dispersion phenomenon may occur by the diffraction phenomenon of light. Since the diffraction phenomenon generally occurs in a hole of a size equal to or smaller than about twice the wavelength of light, the diameter of the hole is preferably one micrometer or longer as the wavelength of visible light is approximately around 0.5 um (500 nm).
Although it is shown in
In
The height h of the substrate 321 of the microlens array layer 310 is equal to the focal length of the microlens 311. The focal length is determined by the radius of curvature and the refractive index of the microlens 311. The focal length f of a microlens 311 having a structure flat at one side and protruding at the other side (plano-convex structure) may be obtained by the mathematical expression shown below.
f=r/(n−1)
The diameter d of the microlens 311 is determined by the focal length f, the width w of the photodiode region 410 of the image sensor 400, and the distance from the hole 321 to the photodiode region 410. Alternatively, if the diameter d of the microlens 311 is determined, the distance from the hole 321 to the photodiode region 410 may be determined considering the focal length f and the width w of the photodiode region 410. Although the focal length varies according to the material (i.e., the refractive index) of the microlens 311, the resolution of the image sensor 400, the pixel size and the like, the focal length may be set to be several micrometers to tens of micrometers approximately, and accordingly, the microlens array layer may be formed to have a thickness of approximately several micrometers to tens of micrometers. Accordingly, the distance from the fingerprint to the fingerprint sensor may be reduce greatly in comparison with conventional techniques, and a display device combined with a fingerprint recognition sensor including the microlens array layer can be formed merely through a semiconductor process.
According to embodiments, a light blocking wall 313 for blocking the light passing through the microlens not to enter any other cells may be provided in the optical layer 300.
According to embodiments, a light blocking layer 315 for blocking the light passing through the microlens not to enter any other cells may be provided in the portions on the top surface of the substrate 312 of the optical layer 300, where the microlenses 311 are not formed.
Meanwhile, according to embodiments, it may be configured, in the embodiment of
Next, some embodiments of forming a microlens array layer including a plurality of microlenses will be described with reference to
As shown in
For example, a thermal reflow method or a 3D diffuser lithography method may be used as a method of forming the master mold.
According to embodiments, a microlens array may be formed by performing only the steps (a) and (b) of
Meanwhile, as a method of forming the light blocking wall in the microlens array layer 310 in the embodiments of
In addition, as a method of forming the light blocking layer 315 on the microlens array layer 310 in the embodiments of
The features, structures, effects and the like described in the above embodiments are included in an embodiment of the present invention and not necessarily limited to only one embodiment. Furthermore, the features, structures, effects and the like illustrated in each embodiment may be combined or modified for other embodiments by those skilled in the art. Accordingly, contents related to the combination and modification should be interpreted as being included in the scope of the present invention.
Although the present invention has been described above focusing on the embodiments, this is only an example and does not limit the present invention, and it is to be appreciated that those skilled in the art may make various modifications and applications not mentioned above without departing from the essential characteristics of the embodiments. For example, each constitutional component specifically shown in the embodiments can be modified. In addition, the differences related to the modifications and applications should be interpreted as being included in the scope of the present invention defined by the appended claims.
DESCRIPTION OF SYMBOLS
-
- 100: Cover layer
- 200: Display panel
- 300: Optical layer
- 310: Microlens array layer
- 311: Microlens
- 312: Substrate
- 320: Aperture layer
- 400: Image sensor
- 410: Photodiode region
- 420: Dummy photodiode region
- 430: Circuit and connection unit region
Claims
1. A display device comprising:
- a cover layer,
- a display panel disposed under the cover layer;
- an optical layer disposed under the display panel; and
- an image sensor disposed under the optical layer.
2. The device according to claim 1, wherein the optical layer includes:
- a microlens array layer including a plurality of microlenses; and
- an aperture layer disposed under the microlens array layer and provided with a plurality of holes spaced apart from the microlenses as much as a focal length of the microlenses.
3. The device according to claim 2, wherein the microlens array layer is provided with a transparent or translucent substrate and a plurality of microlenses formed to protrude on a top surface of the substrate.
4. The device according to claim 3, wherein the substrate has a thickness making a distance from the microlens to the hole be equal to the focal length, and the aperture layer is formed to be attached on a bottom surface of the substrate.
5. The device according to claim 2, wherein the microlens array layer is provided with a transparent or translucent substrate and a plurality of microlenses formed to protrude on a bottom surface of the substrate.
6. The device according to claim 2, wherein the substrate further includes a light blocking wall formed between the microlenses.
7. The device according to claim 2, wherein a light blocking layer is formed in portions of the top surface of the substrate, where the microlenses are not formed.
8. The device according to claim 2, wherein a diameter of the hole is one micrometer or larger.
9. The device according to claim 2, wherein the display panel is an organic light emitting diode (OLED) panel.
Type: Application
Filed: Aug 14, 2018
Publication Date: May 20, 2021
Applicant: HiDeep Inc. (Seongnam-si, Gyeonggi-do)
Inventors: Bon Kee KIM (Seongnam-si, Gyeonggi-do), Young Ho CHO (Seongnam-si, Gyeonggi-do)
Application Number: 16/623,031